The present invention relates to a new .alpha.-amylase inhibitor from wheat (WAI-53) a method for the preparation thereof, and a method of quantitative analysis of .alpha.-amylase isozymes in body fluid using the said .alpha.-amylase inhibitor of the present invention.
.alpha.-amylase is a hydrolytic enzyme widely distributing in living organisms. Human .alpha.-amylases are mainly produced by salivary gland and pancreas and are known to vary considerably in quantity in certain diseases such as pancreatitis, parasynanche, liver diseases, cancer and the like. Accordingly it is desired, for the precise diagnosis of such diseases, to have a method of quantitative analysis not only of total .alpha.-amylase in serum but also of each of the .alpha.-amylase isozymes produced by salivary gland and pancreas.
In clinical laboratories, electrophoretic method is currently used for the discriminative assay of human .alpha.-amylase isozymes. However, the method is too complicated to permit easy and quick assay of clinical samples, and requires skill for the evaluation of the results.
To overcome these difficulties, a process had been developed by O'Donnell et al wherein an .alpha.-amylase inhibitor from wheat is utilized. The process is, however, not really satisfactory and not quite of practical use. [Clin. Chem., 23, 23, 560-566 (1977)].